feat: add pedantic subject validation and max payload enforcement on PUB

Move max payload validation from the parser to ProcessPubAsync so the
server sends -ERR 'Maximum Payload Violation' and closes the connection
(matching Go reference client.go:2442). In pedantic mode, reject PUB
with wildcard subjects via -ERR 'Invalid Publish Subject' (client.go:2869).
Add disposed guard to SubList.Remove to prevent crash during shutdown.

src/NATS.Server/Protocol/NatsParser.cs

@@ -203,10 +203,10 @@ public sealed class NatsParser
             throw new ProtocolViolationException("Invalid PUB arguments");
         }
 
-        if (size < 0 || size > _maxPayload)
+        if (size < 0)
             throw new ProtocolViolationException("Invalid payload size");
 
-        // Now read payload + \r\n
+        // Now read payload + \r\n (max payload enforcement is done at the client level)
         buffer = buffer.Slice(afterLine);
         _awaitingPayload = true;
         _expectedPayloadSize = size;
@@ -253,7 +253,7 @@ public sealed class NatsParser
             throw new ProtocolViolationException("Invalid HPUB arguments");
         }
 
-        if (hdrSize < 0 || totalSize < 0 || hdrSize > totalSize || totalSize > _maxPayload)
+        if (hdrSize < 0 || totalSize < 0 || hdrSize > totalSize)
             throw new ProtocolViolationException("Invalid HPUB sizes");
 
         buffer = buffer.Slice(afterLine);